The present invention relates to a method for preparing spherical microparticles which consist entirely or partly of at least one water-insoluble branchings-containing polyglucan, and also to microparticles obtainable by said method.
The applicant""s German patent application No. 19737481.6 which has earlier priority but is not a prior publication describes methods for preparing spherical microparticles containing water-insoluble linear polysaccharides. This method can produce spherical microparticles which stand out in particular due to high uniformity with respect to their shape and their diameter distribution and also due to good mechanical properties.
Owing to their comparatively uniform composition, at the same time, with good mechanical properties, these particles may be employed for a multiplicity of applications.
The starting material used for the method described therein are linear water-insoluble polysaccharides such as, for example, polyglucans which have no branchings or in which conventional methods of measurement cannot detect branchings. Natural linear polysaccharides and polyglucans, however, are not pure. They have therefore either to be isolated or prepared from native sources such as, for example, starch by means of complicated methods or to be obtained via biotechnological methods.
In particular, purifying polysaccharides of natural, for example plant, origin to give compounds with the high linearity required is comparatively time-consuming and costly, so that natural sources have only been of limited use up until now. In view of their general availability and cost-effectiveness, however, extensive usage of the natural sources is desirable.
Surprisingly, it has been found that using polyglucans containing branchings can also produce qualitatively satisfactory spherical microparticles which may be successfully employed for a multiplicity of applications.
Thus, the present invention relates to a method for preparing spherical microparticles which consist entirely or partly of at least one water-insoluble polysaccharide, wherein the at least one water-insoluble polysaccharide is dissolved in a solvent or solvent mixture, the solution formed is introduced into a precipitant or precipitant mixture, the mixture resulting therefrom is cooled, where appropriate, and the microparticles formed are removed, which comprises selecting the water-insoluble polysaccharide from among a branchings-containing polyglucan, which has a degree of branching of greater than zero and not more than 8%, and a mixture of a branchings-containing polyglucan and a linear polysaccharide, in which mixture the proportion of branchings-containing polyglucans is not higher than 30% by weight with respect to the combined weight of the polysaccharide and polyglucan.
The replacement according to the invention of at least part of the linear starting compounds by branchings-containing polyglucans means a substantial simplification and cost reduction of the method described in application No. 19737481.6. The method of the invention simplifies in particular the exploitation of natural polyglucan sources, which makes a cheap and renewable source of raw materials usable for the present invention.
In this respect, the present invention means an advantageous inventive development of the abovementioned German patent application No. 19737481.6.
For the purposes of the present invention, the disclosure of the German patent application No. 19737381.6 is incorporated in its entirety.
The present application further relates to microspherical particles obtainable by the method of the invention.